Semiconductor memory devices for storing data may be classified into volatile memory devices and non-volatile memory devices. The volatile memory devices are typically configured to store data by charging or discharging capacitors in memory cells, and widely applied as main memories of various electronic apparatus in operation. However, the application of the volatile memory devices are limited since the volatile memory devices retain stored data while power is supplied to the electronic apparatus and lose the stored data when the power is off. In addition, as continuous development of integrated circuit technology, the volatile memory devices face a technology difficulty in scaling down.
Therefore, the non-volatile memory devices, such as flash memory devices and resistive memory devices, have attracted the attention of many researchers. In particular to the resistive memory devices, which have the advantages of compatible with the existing transistors process, are considered as a key candidate for advanced technology in 20 nm or narrower nodes. The resistive memory devices are formed of an array of resistors with resistive elements where each element has two or more stable resistive states. Voltage pulses, which are controlled by the transistors electrically connected to the resistive elements, are typically used to switch the resistive elements from one resistance state to the other. A resistor-forming process applied to the resistive elements is necessary to initialize the resistive memory devices since materials of the resistive elements are inherently insulating. Through the resistor-forming process, conductive pathways will be respectively formed in the resistive elements, so that a high resistance state or a low resistance state of the resistive elements is formed for the data-storing applications.
However, with the increasing requirements of data storing, the amount of resistive elements of the resistive memory array significantly increases in the manufacturing process. The time required to complete the resistor-forming process extends, and the current/voltage required to perform the resistor-forming process also increases. Therefore, it raises the risk of damaging the transistors, which are electrically connected to resistive elements. The issue of reliability of each resistive element of the resistive memory array becomes worse under this circumstance. Accordingly, improvements in methods of fabricating a resistive memory array continue to be sought.